Before induction, with firm occlusive pressure held on both the radial and ulnar arteries, the patient is asked to clench his or her fist several times until the palmar skin is blanched. The patient is then instructed to unclench the fist, and then ulnar artery pressure is released while maintaining occlusion of the radial artery. Overextension of the hand and wide spreading of the fingers should be avoided because it can lead to falsely abnormal results. The time required for palmar capillary refill is noted. An abnormal Allen test result was defined as a recovery time of more than 10 seconds.

Ultrasonography measurements will be performed with a linear probe. The non-dominant hand of the patient will be fixed in the anatomical position on the arm chair. The wrist joint of patient will be extended to 30 degree with a wrist pad. The Ultrasonography probe will be transversally placed 2 cm proximal to the styloid process and the short axes of the radial artery will be scanned. The diameter of the radial artery will be measured and recorded.

Before induction, with firm occlusive pressure held on both the radial and ulnar arteries, the patient is asked to clench his or her fist several seconds until the palmar skin is blanched. The patient is then instructed to unclench the fist, and then ulnar artery pressure is released while maintaining occlusion of the radial artery. The time required for palmar capillary refill is noted. An abnormal Allen test result was defined as a recovery time of more than 10 seconds. Ultrasonography measurements will be performed with a linear probe. The non-dominant hand of the patient will be fixed in the anatomical position on the arm chair. The wrist joint of patient will be extended to 30 degree with a wrist pad. The USG probe will be transversally placed 2 cm proximal to the styloid process and the short axes of the ulnar artery will be scanned. The blood fow of ulnar artery will be measured and recorded.